since passage of the Americans with Disabilities Act (ADA), increasing amounts of attention have been directed to improving safety conditions for the disabled in the home and in the workplace. One of the areas of great concern is the production of fire and smoke detection devices for the hearing impaired. It is well recognized that traditional audible fire and smoke detection devices are often insufficient to warn persons having hearing disabilities of the presence of fire hazards. To counteract this problem, various different alarm systems have been employed including flashing light, vibration and air movement systems.
U.S. Pat. No. 4,649,376 discloses a fire alarm system consisting of both visual and audible components. A smoke detector unit is mounted on the ceiling of a hallway. The smoke detector unit generates an audible alarm to alert occupants that the level of smoke in the hallway is excessive. Lamp units are provided in the hallway to provide visual directional signals for directing occupants to an exit. The lamp units are positioned in a lower region of the hallway such that they are in a region of minimum smoke. To facilitate escape in case of fire, it is recommended that occupants drop to the floor and follow the lamp units and crawl to the nearest exit.
Although the forgoing fire alarm system consists of audible and visual components, the visual components are used only as directional signals to direct occupants to exits after the occupants have been alerted of the presence of a fire hazard. The occupants are actually alerted of the fire hazard by the audible alarm. A severe risk of injury is presented if the audible alarm is not effective to alert the occupants. Thus, it is desirable to provide a visual alarm device to alert occupants of the presence of a fire hazard.
The Underwriters Laboratories, Inc. (UL) published standards for luminous intensity of light based alarms in a publication entitled, "Standard for Signaling devices for the Hearing Impaired" UL 1971, First Edition, Jun. 30, 1992 which is herein incorporated by reference. The UL standard tracks luminous intensity along vertical and horizontal arcs about a light emitting device as depicted in FIG. 1. When designing a device to generate an intensity profile that matches a desired standard, several factors must be considered such as the intensity of the light source and the position of the light source. Often, fire alarms operate on back-up battery power because primary power is unavailable. Thus, it is desirable to keep power consumption to a minimum. A most efficient system will consume only enough energy to create an intensity profile that substantially follows the UL standard.